Do Atoms Exist in a Perfect Vacuum?

[brainstorm]

The answer to "why" is that this is how people communicate, words are "arbitrary" and mean what we (by consensus) want them to mean.
The word "vacuum" simply mean absence of matter, and the reason for this is that it is how the word has been used for the part 200 years or so. This is a question of etymology; not philosophy. As far as I know there is no word that means "absence of EM radiation", but of course there is nothing that prevents you from making one up.

I gave you the definition from three sources. It does not involve EM radiation.

This is essentially the issue of whether scientific terminology and concepts are (or should be) based on traditional authority or rational authority. If there is no basis except tradition for scientific terms and concepts, why should anyone ever subject them to critical rigor in any form. Shouldn't theories then simply be accepted by definition and contradictions and other problems within them ignored?

If vacuum is traditionally defined as the absence of matter, fine, but why would that be the end of the story? Vacuum is not an arbitrary concept. It has specific analytical uses that make it relevant. If you aren't open to understanding and discussing these, what kind of science are you really engaged in?

Now if you want to give me another source that shows a vacuum is connected to radiation levels I will happily consider your above statement.

This isn't a contest of proving one definition is more established than another. It is about dissecting the concept of "vacuum" to understand it better, why or why not radiation and/or force should be considered in terms of vacuum-analysis, and why.

Until then, we'll stick with the agreed upon definition.

How about "we" stick with discussing the topic and avoid making statements that imply collective domination, like "we vs. others." This is an aggressive discussion style.

The "relevant issue" as you put it is not why, that question has never been raised. Besides, a vacuum is simply a way of describing a system where there is no / little matter - it doesn't need to mention radiation because that isn't what is being described.

Now you're saying that it is irrelevant for someone to ask a scientific question about vacuum-operationalization because of definitional traditions? Why shouldn't Galileo have just submitted to the traditional definition of the heavens as being all massive bodies surrounding the Earth and therefore continued to analyze the heavens as centered around the Earth? His science was to explore reasons that it might make analytical sense to define planetary-motion in another way. Even if he would have been wrong, there was no reason to chastize him for exploring the issue.

 

[brainstorm]

So, given the definition, as meaning, the absence of matter but not necessarily the absence of electromagnetic radiation, can eletromagnetism have any affect on the velocity of light?

I'm not claiming to be able to answer this but I want to add something to your question because I think it is interesting. If electromagnetism wouldn't have any effect on the speed of light, how could light slow down in a medium whose volume primarily consists of atomic/molecular electrons?

 

[JaredJames]

Brainstorm, a vacuum is an area devoid of matter. That's it. That's why it's the end of the story.

It's not meant to describe the radiation content. It deals purely with matter.

The scientific label for an area that lacks matter is a vacuum.

If you want to create a word to deal with the lack of radiation then go ahead.

Please take your philosophical questions to the philosophy section. Stick to the scientifically accepted definitions here.

 

[JaredJames]

I'm not claiming to be able to answer this but I want to add something to your question because I think it is interesting. If electromagnetism wouldn't have any effect on the speed of light, how could light slow down in a medium whose volume primarily consists of atomic/molecular electrons?

Because electrons have mass. They are, matter.

 

[brainstorm]

Brainstorm, a vacuum is an area devoid of matter. That's it. That's why it's the end of the story.

It's not meant to describe the radiation content. It deals purely with matter.

The scientific label for an area that lacks matter is a vacuum.

If you want to create a word to deal with the lack of radiation then go ahead.

Please take your philosophical questions to the philosophy section. Stick to the scientifically accepted definitions here.

Wouldn't insisting on definitions and the reasons for accepting them also belong in the philosophy section then? If someone in the thread brings up the issue of whether a vacuum can or should also be free of radiation and/or force, why shouldn't the scientific issues related to that be discussed? You avert this discussion by making it purely about definitions. This is obstructing scientific discussion, isn't it?

 

[brainstorm]

Because electrons have mass. They are, matter.

So what's your point? You make statements without grounds or reasons. Do you think discussion is about establishing definitions and other labels? If electrons have mass and are matter, how does that relate to the question of whether they affect the speed of light? You need to address that specifically. If you are trying to say that their electromagnetism is irrelevant to the speed of light, then say that and explain why. Stop just making insistent statements that assert your point of view without reasonable grounds.

 

[JaredJames]

So what's your point? You make statements without grounds or reasons. Do you think discussion is about establishing definitions and other labels? If electrons have mass and are matter, how does that relate to the question of whether they affect the speed of light? You need to address that specifically. If you are trying to say that their electromagnetism is irrelevant to the speed of light, then say that and explain why. Stop just making insistent statements that assert your point of view without reasonable grounds.

You said: "If electromagnetism wouldn't have any effect on the speed of light, how could light slow down in a medium whose volume primarily consists of atomic/molecular electrons?"

Light slowing through a medium made of electrons has nothing to do with their EM properties, only the fact they are matter.

My post responded to your question.

 

[JaredJames]

Wouldn't insisting on definitions and the reasons for accepting them also belong in the philosophy section then?

Yes it should, but I'm not debating whether they should be accepted. Only that they are what they are and for the purpose of this discussion that's what matters.

If someone in the thread brings up the issue of whether a vacuum can or should also be free of radiation and/or force, why shouldn't the scientific issues related to that be discussed?

Because once again, a vacuum does not deal with EM radiation.

You avert this discussion by making it purely about definitions. This is obstructing scientific discussion, isn't it?

Scientific definitions.

Do you accept that the word vacuum only deals with the lack of matter? Do you accept it is a way of describing a system that lacks / or has little matter?

EM radiation is irrelevant when it comes to vacuums. The 'why' of that is simply because it is the accepted scientific definition.

 

[santhony]

Can I confirm that you understand light is EM radiation? And that all EM radiation travels at that constant speed?

As I said before, physics is not my expertise. But, I do find it fascinating. I am aware of the fact, that, all electromagnetic radiation is light vibrating at various frequencies; so, it would make sense to say all electromagnetic radiation shares a constant speed. So, I guess my question, in that regard, is nonsensical.

 

[Drakkith]

I'm not claiming to be able to answer this but I want to add something to your question because I think it is interesting. If electromagnetism wouldn't have any effect on the speed of light, how could light slow down in a medium whose volume primarily consists of atomic/molecular electrons?

I've read that this is because the photons are continually absorbed and re-emitted, which takes a small amount of time, thus making the average velocity throughout the material slower than c. The light still travels at full speed between the time it is emitted and the time it is reabsorbed.

 

[mheslep]

I've read that this is because the photons are continually absorbed and re-emitted, which takes a small amount of time, thus making the average velocity throughout the material slower than c. The light still travels at full speed between the time it is emitted and the time it is reabsorbed.

Common mistake.

This explanation is incorrect and inconsistent with empirical observations.

https://www.physicsforums.com/showpost.php?p=899393&postcount=4

 

[Drakkith]

Mheslep, from the post you linked:

So the lattice does not absorb this photon and it is re-emitted but with a very slight delay.

So isn't this the same thing as I said above, but instead of the individual atoms absorbing the photons it's the lattice? Or am I not understanding something?

 

[mheslep]

Mheslep, from the post you linked:
So isn't this the same thing as I said above, but instead of the individual atoms absorbing the photons it's the lattice? Or am I not understanding something?

I would not attempt to elaborate on the clear and precise FAQ article by ZapperZ, Gokul43201 and inha. You might PM one of the authors if you don't see further response in thread.

 

[thopsy]

A perfect vacuum is a finite area with zero mass (no atoms, or other massive particles, protons, neutrons, electrons, positrons, etc...).

Electromagnetic radiation is composed of photons, which, to my understanding, have zero mass. Therefore, you certainly can have electromagnetic radiation in a vacuum.

Additionally, photons like vacuums the best. That's where they travel at the speed of light!

 

[Drakkith]

I would not attempt to elaborate on the clear and precise FAQ article by ZapperZ, Gokul43201 and inha. You might PM one of the authors if you don't see further response in thread.

Alright, thanks for the link!

A perfect vacuum is a finite area with zero mass (no atoms, or other massive particles, protons, neutrons, electrons, positrons, etc...).

Electromagnetic radiation is composed of photons, which, to my understanding, have zero mass. Therefore, you certainly can have electromagnetic radiation in a vacuum.

Additionally, photons like vacuums the best. That's where they travel at the speed of light!

So do you think photons prefer Hoover or Oreck vacuums better? =)

 

[thopsy]

Let's be clear on something...electromagnetic radiation, i.e. electromagnetic waves, is composed of photons (no mass), not electrons (which have mass).

 

[thopsy]

@Drakkith...neither. Photons like Dyson all the way.

 

[JaredJames]

So do you think photons prefer Hoover or Oreck vacuums better? =)

Dyson, any day of the week!

 

[JaredJames]

@Drakkith...neither. Photons like Dyson all the way.

Dyson, any day of the week!

It's unanimous.

 

[Drakkith]

@Drakkith...neither. Photons like Dyson all the way.

Touche...

 

[thopsy]

One more thing...the change in the speed of light is due to a change in the "phase velocity", i.e. the speed of the propagating wavefront, and not the velocity of the photons.

 

[Drakkith]

One more thing...the change in the speed of light is due to a change in the "phase velocity", i.e. the speed of the propagating wavefront, and not the velocity of the photons.

I'm assuming that they aren't one in the same?

 

[thopsy]

Jeez, I hope not. My knowledge ends here. :(

 

[capanni]

The answers on the definition of a vacuum and a perfect vacuum tell you about atoms existing in a vacuum. Electromagnetic radiation can pass though a vacuum, otherwise as soon as a wave encountered a volume of perfect vacuum, what would happen to it?
Given the low density of atoms in space, and decreasing in interstellar space this would kind of mess with the electromagnetic waves we need to observe the universe with.

You can also consider the occurrence of
1) blackbody photons

2) vacuum fluctuations which are virtual particles that appear and disappear in a vacuum, observed via the Casimir effect of quantum field theory.

 

[santhony]

So, in saying, a "perfect vacuum" is defined as having no matter, is the space around atoms void of matter? And, if so, would that mean atoms exist in a vacuum?

 

[JaredJames]

So, in saying, a "perfect vacuum" is defined as having no matter, is the space around atoms void of matter? And, if so, would that mean atoms exist in a vacuum?

You're referring to the spaces within the atom itself? Between the nucleus and electron etc?

 

[santhony]

You're referring to the spaces within the atom itself? Between the nucleus and electron etc?

No. Honestly, I'm referring to the space surrounding an atom.

 

[JaredJames]

No. Honestly, I'm referring to the space surrounding an atom.

What space would that be then if it isn't the space of the atom itself?

 

[santhony]

Is there no space surrounding atoms? I was told by someone, who says he has a Bachelor's Degree in Physics, "the spaces between atoms -- even in a solid -- contain nothing but empty space. So there's lots of vacuum all over the place." Is this true?

 

[JaredJames]

Is there no space surrounding atoms? I was told by someone, who says he has a Bachelor's Degree in Physics, "the spaces between atoms -- even in a solid -- contain nothing but empty space. So there's lots of vacuum all over the place." Is this true?

Yes, the atoms are 'surrounded by empty space' - this is the part relating to the electrons.